Process for the manufacture of gaseous discharge lamps



PROCES S FOR THE MANUFACTURE OF GASEOUS DISCHARGE LAMPS Filed Sept. 26,1941 RELATIVELY SHORT LENGTH I FLUORESCENT TUBING I HIGHLY EVACUATEDOPERATED FIRSTAT APPROXIMATELY 20D MILLIAMPERES THEN AT 300-350M'LLIAMPERES igjLuoREscENT TUBI 60F FINAL LENGTH HIGHLY EVACUATEDPREVIOUSLY TREA,T,E0 IN SHORT TUBE OPE RATED FIRSTAT APPROXIMATELY 350MILLIAMPERES THEN AT 500-600 MILLIAMPERES [wmwl PREVIOUSLY TREATEDF'INTL LENGTH TUBING 16 WITH TNsTALLEn ELECTRODES T NOW GAS, FILLEDOPERATEDAT APPROXIMATELY SOMILLIAMPERES FOR FROM 15 20 MINUTES BY v ATTORNE K Patented JulyZl, 1942 UNITED STATES PATENT OFFICE PROCESS FORTHE MANUFACTURE OF GASEOUS DISCHARGE LAMPS Eugene A. Quarrie, Scarsdale,N. Y. Application September 26, 1941, Serial No. 412,486

Claims.

The invention relates to the manufacture of gaseous discharge lamps andis particularly adapted to the manufacture of the fluorescent type ofluminous lamp.

In the manufacture of these lamps and particularly the cold-cathodefluorescent type, the electrodes between which the discharge occurs areinstalled directly in the tube or other transparent envelope orcontainer for the gaseous medium. In the initial operation of such lampthe occluded gases of the electrode material as well as other impuritiesare released and the wall of the envelope, particularly the fluorescentcoating thereof, is bombarded therewith. A film or deposit is therebyintroduced which is more pronounced on such coating, and more especiallyas a result of the formation of an amalgam from the mercury ormercury-vapor contained in the envelope. This causes discoloration anddarkening of the otherwise luminous portion of the tube which may extenda substantial distance 'along the tube from each of the electrodes,eventually travelling the entire length of the tube. The efliciency ofsuch lamp is thereby greatly diminished and the light emission graduallyreduced.

It is an object of the present invention to provide a novel process forpreparing such lamps whereby a clean, clear tube or envelope ismaintained so that an efficient lamp of relatively long life results.

A further object of the invention is to provide a lamp permitting of theuse of higher operating current, due to lower electrode resistance, thanhas heretofore been found commercially practicable, as well as toeliminate rippling and snaking effects.

In carrying out the invention, the electrodes utilized in the lamp aregiven an initial processing or forming exteriorly thereof, as in apreparparatory tube, to remove organic and other deleterious impuritiesso far as possible, after which they are installed in the lamp andfurther formed.

The nature of the invention, however, will best be understood whendescribed in connection with the accompanying drawing,which illustratesmore or less diagrammatically various stages in the formation of theelectrodes in their application to a gaseous discharge lamp, Fig. 1showing a relatively short length of tubing wherein the electrodes areinitially processed, and Figs. 2 and 3 the electrodes installed in thefinal lamp wherein they are furtherprocessed, as indicated in Fig. 2,and aged as indicated in Fig. 3.

Referring to Fig. 1 of the drawing, the electrodes for use in the finallamp are indicated at is and II and as mounted in an envelope H which ispreferably a short length of tubing evacuated to a high degree. Thistubing may be clear on itsinner surface or coated with a fluorescentmaterial. In accordance with the invention, these electrodes, which arecoated with the usual materials such as barium and strontium carbonatesand are in all respects constructed as for use in known luminescentlighting, are located only temporarily in the particular envelope ii foran initial processing thereof. This includes efiecting an intensiveelectrical discharge therebetween, provided by a transformer I3, andinitially maintained at approximately 200 milliamperes until the orchidcolor of the discharge resulting from water and other common vaporsdisappears. Thereupon, the current is increasedto from 300 to 350milliamperes until such time as the electrodes III, II become heated toa bright cherry red color and the discharge itself attains theflickering stage. The discharge is then discontinued and the tubeallowed to cool.

After the tube hascooled sutflciently, the electrodes are removedtherefrom, said partly processed electrodes I5 and I6 then beingindicated as located in the final envelope or tubing ll of the desiredlength and constituting the lamp in its final form, the electrodes beingintended for permanent installation therein. After this envelope, hasbeen highly evacuated, a discharge is again affected between theelectrodes, as from the transformer 18, until the orchid color ofdischarge then disappears. The initial current is approximately of theorder of magnitude of 350 milliamperes which is increased, after thedisappearance of the orchid color, to from 500 to 600 milliamperes anduntil the electrodes show a cherry to bright red color with the tubebeing heated to a degree just suflicient to carbonize paper laid againstthe tube.

After discontinuing the discharge, the tube is allowed to cool and issealed 0!! from the source of vacuum (not shown). There is thenintroduced at the proper pressure the required rare gas in accordancewith the particular color of the emitted light desired, as is wellunderstood in the art. Mercury is then released into the tube in theusual manner and when the tube has been aged, it is ready for service.The aging may be effected by passing through the tube, for from fifteento twenty minutes, a current of substantially milliamperes fromtransformer l8, or until themercury vapor is evenly distributed in thetube which then assumes a uniform brilliancy.

I claim:

1. In the manufacture of luminescent lamps: the steps of treating theelectrodes for use in the final lamp in a preliminary tubing under highvacuum by first efiecting an intensive discharge therein between thesaid electrodes, then increasing the intensity of the discharge,discontinuing the discharge and allowing the tube to cool, removing theelectrodes from the preliminary tubing and installing the same in thefinal tube, operating the final tube under a high degree of vacuum, thenincreasing the intensity of the discharge, discontinuing the dischargeand allowing the tube to cool, then sealing off the same, introducingthe desired gaseous medium,- and finally aging the tube.

2. In the manufacture of luminescent lamps: the steps of treating theelectrodes for use in the final lamp in a preliminary tubing under highvacuum by first efiecting an intensive discharge therein between thesaid electrodes, th'en increasing the intensity of the discharge,discontinuing the discharge and allowing the tube to cool, removing theelectrodes from the preliminary tubing and installing the same in thefinal tube, operating the final tube under a high degree of vacuum, thenincreasing the intensity of the discharge, discontinuing the dischargeand allowing the tube to cool, then sealing of! the same, introducingthe desired gaseous medium, releasing mercury into the tube, and finallyaging the tube.

3. In the manufacture of luminescent lamps: the steps of treating theelectrodes for use in the final lamp in a preliminary tubing under highvacuum by first effecting an intensive discharge therein between thesaid electrodes at approximately 200 milliamperes, then increasing theintensity of the discharge to from 300 to 350 milliamperes,discontinuing the discharge and allowing the tube to cool, removing theelectrodes from the preliminary tubing and installing the same in thefinal tube, operating the final tube under a high degree of vacuumsubstantially at 350 milliamperes, then increasing the intensity or thedischarge to from 500 to 600 milliamperes, discontinuing the dischargeand allowing the tube to cool, then sealing off the same, introducingthe desired gaseous medium, and finally aging the tube by passing acurrent of substantially milliamperes therethrough.

4..In the manufacture of luminescent lamps: the steps of treating theelectrodes for use in the final lamp in a preliminary tubing under highvacuum by flrst eflecting an intensive discharge therein between thesaid electrodes at approximately 200 milliamperes, then increasing theintensity of the discharge to from 300 to 350 milliamperes,discontinuing the discharge and allowing the tube to cool, removing theelectrodes from the preliminary tubing and installing the same in thefinal tube, operating the final tube under a high degree of vacuumsubstantially at 350 milliamperes, then increasing the intensity of thedischarge to from 500 to 600 milliamperes, discontinuing the dischargeand allowing the tube to cool, then sealing off the same, introducingthe desired gaseous medium, releasing mercury into the tube, and finallyaging the tube by passing a current of substantially 60 milliamperestherethrough.

5. In the manufacture of luminescent lamps: the steps of treating theelectrodes for use in the final lamp in a preliminary tubing under highvacuum by first eiIecting an intensive discharge therein between thesaid electrodes at approximately 200 milliamperes and until the orchidcolor of the discharge disappears, then increasing the intensity of thedischarge to from 300 to 350 milliamperes and until the electrodes areheated to a bright cherry red color and the discharge reaches aflickering stage, discontinuing the discharge and allowing the tube tocool, removing the electrodes from the preliminary tubing and installingthe same in the final tube, operating the final tube under a high degreeof vacuum substantially at 350 milliamperes and until the orchid colorof discharge again disappears, then increasing the intensity of thedischarge to from 500 to 600 milliamperes and until the electrodes showa cherry to bright red color and the tube heats to a degree justsuflicient to carbonize paper, discontinuing the discharge and allowingthe tube to cool, then sealing oil the same, introducing the desiredgaseous medium, releasing mercury into the tube, and finally aging thetube by passing a current of substantially 60 milliamperes therethroughuntil the mercury vapor is evenly distributed.

EUGENE A. QUARRIE.

